Two-component calculations for the molecules containing superheavy elements: Spin-orbit effects for (117)H, (113)H, and (113)F

We have calculated bond lengths, harmonic vibrational frequencies, and diss ociation energies for (117)H, (113)H, and (113)F using relativistic effecti ve core potentials (RECPs) with one-electron spin-orbit operators at the tw o-component coupled-cluster levels of theory. It is shown that any reasonab le theoretical descriptions of the electronic structures of molecules conta ining superheavy elements require consideration of relativistic interaction s and electron correlations. Comparisons with available all-electron Dirac- Fock (DF) based results indicate that our two-component approaches are very promising tools in the calculations for the molecules containing superheav y elements. The spin-orbit effects calculated from one- and two-component R ECPs are in good agreement with those from all-electron Douglas-Kroll and D F results, implying that the potential average scheme is useful for obtaini ng one- component RECPs even for superheavy elements. Spin-orbit and electr on correlation effects are not additive for molecular properties of (117)H, (113)H, and (113)F, but spin-orbit effects are qualitatively similar at al l levels of theory considered. Spin-orbit effects contract R-e and increase omega(e) for (113)H and (113)F, whereas they expand R-e and decrease omega (e) for (117)H. Spin-orbit effects decrease D-e for all molecules considere d, but the amount of decrease for (113)H and (117)H is substantially smalle r than that estimated from the atomic splittings. For (117)H, our best calc ulations yield 1.983 Angstrom (R-e), 1403 cm(-1) (omega(e)), and 1.60 eV (D -e). (C) 1999 American Institute of Physics. [S0021-9606(99)30418-9].